Lining tubes



Jan. 7, 1941. E. c.' LEONHARDY LINING TUBES Filed Sept. 30, 1938 Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE Edwin C. Leonhardy, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application September 30, 1938, Serial No. 232,578

2 Claims.

The invention particularly relates to an im-l proved method and means of expanding relatively ductile or thin wall liners into tubular metallic elements of greater tensile strength by 5 the'application of internal fluid pressure to the v liner while the latter is in place in said tubular element.

In many industries, tubular elements employed -as conduits for various materials or as reaction l or contact zones are subjected to different conditions of corrosion, erosion, oxidation and the like about their internal and external surfaces and in many instances no single metal or metallic alloy is" suitable for both the internal and ex- 15 ternal conditions to which the same tube is subjected. A typical example of the occurrence of this condition is invheating corrosive uids to relatively high temperatures and/or at higher superatmospheric pressure. Metals and metallic 20 alloys which will resist most forms of corrosion are readily available, although rather expensive in many cases, and various steel alloys, the most commonly used of which is probably nickel-chromium steel, will successfully resist extremely 25 high temperature and pressure conditions.

However, the alloys suitable for high temperature and pressure conditions are by no means resistant to all forms of corrosion. In such instances, th use of a liner or double wall tube is 30 indicated, the outer tube or wall, which comes in contact with the heating medium.'being rela.- tively thick and/or resistant to high temperature and pressure conditions, while the other wall or liner may be relatively thin and composed of 35 an alloy which resists the corrosive conditions to which it is exposed.

In problems of the type above mentioned, the

difllculty resides in uniting the thin wall, noncorrosive liner with the thicker external walls 40 of the tube in such a manner that heat may be readily transferred through both walls. When an air-space or pocket is left between the liner and the thick wall tube, the flow of heat is retarded at this point and will result in poor heat 45 transfer efficiency and relatively hot and relatively cold spots or zones along the tube walls. The advantage of using relatively thin wall liners is readily apparent, since, as previously stated, the cost of non-corrosive and metallic alloys is 50 usually high. A painted, sprayed or baked enameled surface of corrosion-resistant materiall 4applied to the tube has been successful in a few instances, particularly where external corrosion or electrolysis is encountered, but as applied to 55 lining the internal surface Cof relatively small elongated tubular elements it is extremely difficult to obtain an impervious, uniform surface and even then is not satisfactory for all conditions.

Various methods and means of expanding relatively thin liners into tubes have been proposed and tried. One of the methods heretofore used involved inserting a liner in the tube and then forcing or drawing a tapered plug through the liner to expand the same to contact with the walls of the tube. Special devices for rolling or l0 beating the walls of the liner to expand the same against the tube have been tried. The present inventor has been engaged in work of this nature for some time and his experience is that the failure of these previous methods to achieve entirely satisfactory results resides primarily in the eccentricity and non-uniform thickness of the steel and steel alloy tubes available. These tubes are manufactured to a close tolerance on external diameter, but the manufacturing methods employed necessitate a tolerance of some over the specified minimum wall thickness. Tubes of the same heat or batch will vary considerably in wall thickness and the wall thickness ofI each individual wall tube may vary 25 throughouty its length and about its circumference. Spiral depressions are often found in the internal walls dueto the use of a rotating mandrel in drawing the tube. It is virtually impossible to beat, roll or otherwise expand the liner by mechanical means in such a manner that it will conform to the non-uniform condition of the l internal walls of the tube,'particularly in the relatively long -and relatively small diameter tubes ordinarily employed. I have found, however, that by applying a high internal uuid pressure to the liner, while the latter is in place in the tube, it may be expanded to substantially the exact contour of the tube walls despite irregularities and any eccentricity of the tube. I pref- 40 erably employ a relatively incompressible vliquid such as water or oil for this purpose, but air or other compressible fixed gas may be utilized within the scope of the invention.

I have utilized the method and means specified by the invention, of expanding liners into tubes by the application of internal fluid pressure, with a high degree of success, vboth from the standpoint of economy and final results. The process is much more rapid than previous methods and' involves the u'seof ,only relatively simple and inexpensive equipment upon which there is a minimum of wear and replacement'.

The accompanying diagrammatic drawing illustrates one specific form of apparatus in Cil of the apparatus illustrated in Figures 1 and 2,

with the tube and liner in place, this view being taken along the plane indicated by line 3-3 in Figure 1.

A frame for receiving a tube and holding it during the liner expanding operation is provided and comprises side-members I which are standard steel channels with their web spaced apart to provide an opening therebetween for the tube and liner and with their ends welded to heavy steel plates 2. The end plates 2 are reinforced, in the case here illustrated, by transverse metal plates 3 extending across the width of plates 2 and welded to the latter. The channel side members I are transversely braced by one or more steel plates 4 spanning the space therebetween and welded to one flange of each of the channels, the opposite side of the frame being left open so that the tube and`liner may be readily inserted and removed therefrom.

The tube 5, in which liner 6 has been inserted before placing the same in the frame, is heldin place, in the particular case here illustrated, yby suitable set screws 1, the ends of which engage tube at spaced points about its circumference. IWo of the set screws 1, in this particular instance, extend through and are threaded to each of the plates 4, while the set screws on the opposite side of the frame extend through and are each threaded to an angle member 8. Members 8 are releasably engaged with the top flanges of channel members I by means of lugs 23 welded to the latter. As will be apparent from the drawing, members 8 are removable from the assembly when a tube and liner is to be placed within or removed from the frame.

A lug 9, which is attached to or integral with one of the plates 3, acts as a stop for one endl of the liner 6 and the adjacent end of the outer tube 5 abuts suitable stops I0 -attached to channels I at a spaced distance from lug 9, the liner being preferably somewhat longer than tube 5 and extending beyond the opposite ends of the latter, since the length'of the liner will be considerably decreased by its circumferential expansion.

Screws I I, one of which is disposed at each end of the frame, extend through and are threaded to the adjacent end plate 2. The outerend of each of these screws is flattened, as indicated at I2, to receive a wrench for adjusting the same. A metal plug I3 which closely fits and is adapted to slide into liner 6 is provided at the inner end of each of the screws II. By providing adjusting means, such as screws I I, compensation for tubes of varying lengths is obtained so that plugs I3 may be properly located within the liner with reference to the ends of tube 5. This adjustment is not an essential feature of the invention since the tubes to be lined may be cut to uniform length before being inserted in the frame, in which case the position of plugs I3 may be fixed by attaching each of them to a rod, bar or shaft rigidly attached to' the adjacent end plate 2. It is also entirely within the scope of the invention to mount the plug I3 adjacent stops In in fixed relation thereto in the manner above described and employ an adjustable screw II at the opposite end of the frame. Preferably, plugs I3 are located by either adjustableor fixed means so that the inner face of each plug is substantially ush with the adjacent end of tube 5.

To prevent the leakage of fluid from the liner when pressure is applied, pliable cups I4 of leather, rubber, or other suitable material are tively small and preferably flexible tube I5 which is capable of withstanding the pressure employed. This tube is connected to the outer end of one of the screws II by connector I6 and communicates through opening I'I, extending through this screw II and plug I3, and through opening IB in cup I4 with the space in liner 6 between cups I4. As internal pressure is applied to the liner by operation of the pump or compressor, the liner gradually expands and contacts the inner surface of the walls of tube 5, the flanges of cup I4 expandingwith the liner and keeping the pressure zone tightly sealed.

The pressure required to satisfactorily expand the liner and make it conform to irregularities in the internal surface of the tube into which it is expanded will, of course, depend upon the composition, size and strength of the liner, as well as the strength of the outer tube. A pressure in excess of the elastic limit of the liner will, of course, be required and it may also exceed the yield point of the outer tube, but should not too closely approach the elastic limit of the latter. With the foregoing in mind, the minimum and maximum limits of the actual gauge pressure most suitable may be determined by calculations based upon the diameter and wall thickness of the tubes and the known physical properties of the metals or alloys of which they are composed.

As previously stated, I preferably employ hydrost'atic pressure to expand the liner, since the operation may be more quickly performed with less expense than when a compressible fluid is utilized. When hydrostatic pressure is employed the liner preferably is substantially filled with a relatively non-compressible fluid, such as water or oil, and air is vented from the liner before pressure is applied.

In numerous tests, no difliculty has been encountered with ruptured or otherwise damaged tubes or liners as a result of this method and aside from occasional replacement of the cups I 4, no repairs or replacement of equipment have been required. It is Worthy of note that care should be exercised to see that cups I4 are within the space enclosed by the outer tube 5. .If they are allowed to project any substantial distance beyond the ends of tube 5, the liner will expand at this point and there is danger of rupturing the pressure are employed. Although actual failure of the liner under the pressures ordinarily employed is not likely to occur, if the cups are not properly placed expansion of the liner may cause them to creep between the liner and plug I3 and the cup may be ruptured or destroyed.

` liner if pressures in excess of its safe working l In the particular case here illustrated, the entire assembly, above described, is mounted upon legs 24 and 25 attached to opposite ends of the frame. The form o'f the rear legs 24, here illustrated, permits elevation of the forward end of the assembly which is advantageous in venting substantially all of the air from the liner. Since the tube and liner may ordinarily be placed in and more readily removed from the frame when the latter is in a horizontal position, it is normally retained in this position, except when venting air from the lines. In the particular case here illustrated, an eye 26 is attached to the top central portion of the forwardend plate 2 for receiving the hook 21 of a chain fall or the like, not illustrated, which may be used for elevating the forward end of the assembly.

To facilitate venting air from the space within the liner between cups I4, when hydrostatic pressure is employed for expanding the liner, cup I4 and screw Ii at the forward end of the assembly are also provided with openings I8 and Il, respectively, and a tube 20 having a valve 2l or other suitable shut-oil 'means is attached to the outer end of this screw and communicates through openings Iil and I8 with said space.

As a specic example of the operation of the process herein provided, as it"may be accomplished in an apparatus such as illustrated and above described, the tube to be lined is 3% inch O. C.,nickelchromiumsteel tube approximately 15 feet long with a minimum wall thickness of fi; inch. The alloy employed for this tube corresponds to A. S. T. M. speciiication No. 158-37T, except that approximately 0.35% of titanium is added. This alloy is one of the class of commonly termed stainless steel and is advantageously used where high pressures and high furnace temperatures are encountered. .l

The liner employed is a 25/8 inch O. D. tube, approximately 11 feet long with a nominal wall thickness of 1A; inch and is composed of a copperaluminum alloy containing from 92 to 95% copi per, the remaining to 8% being substantially entirely aluminum.

The outer surface of the liner is carefully wiped to remove any foreign material and, preferably, the inner surface of the steel alloy tube is swabbed for the same reason. 'Ihe liner is then inserted in the outer tube and the two are set within the vframe in the position shown in Figure 1 of the accompanying drawing with each end of the liner projecting at a suillcient distance from the end of the outer tube to compensate for shrinkage in the length Yof the liner as it expanded. The cups I4 and plungers I3 are inserted in opposite ends of the liner to ap\ proximately the position shown in Figure 1. 'I'he assembly ls'then up-ended, valve 2l at the high end is opened and cold water is admitted from a high pressure pump to the liner to ll the same and expel the air through valve 2|. Whenh a steady stream of water flows through valve 2 I, the latter is tightly closed and by continued operation of the high pressure pump the pressure within the liner is gradually increased to approximately 6,000 pounds per square inch, auge pressure. vWhen this pressureis reached. the pump is stopped and valve 2I is opened to relieve the pressure. Plungers I3 are then backed from the liner, the upper set screws 'I loosened, members 22 disengaged from lugs 23 and removed and the lined tube is then removed from the frame. In case cups I4 are not attached to plungers I3 or lhave not been forced from the liner by water expelled therefrom, they are not recovered with a packing hook or the like and the apparatus is ready to receive another tube and liner.

It was noted during this operation that the pump rapidly builds up a pressure of approxi mately 2,000 pounds but that the rate of pressure increase from approximately 2,000 to 4,000 pounds is relatively slow, the rate of pressure increase being again relatively rapid from about 4,000 to 6,000 pounds. This indicates that the actual expansion of the liner takes place between approximately 2,000 and 4,000 pounds. Micrometer measurements on the outer tube indicate that it is expanded by about 0.005 of an inch, while the full 6,000 pounds pressure is applied, but that when this pressure is released the tube returns to its normal size.

Without any particular haste or eiort to establish a record, the entire tube expanding operation, above described, was accomplished in approximately 12 minutes time using a hand-operated pressure pump. Obviously, this time could be materially shortened by the use of a motor driven pressure pump. Automatic controls for opening and closing valves 2.I would further re-l duce the time required. This compares with a time of approximately 1 hour for expanding the liner by drawing or forcing a tapered plug therethrough and a time of approximately 4 to 6 hours for expanding the liner with special beating, spinning, or rolling equipment. For large scale operations or quantity production, I contemplate the use of a frame, such as illustrated and above described, but having a multiplicity of tube compartments with header arrangements for simultaneously supplying fluid under high pressure to the interior of each of the liners so that a multiplicity of tubes may be lined in a single pressurizing operation.

I claim as my invention:

l. An apparatus for expanding liners into tubes which comprises, in combinationl, a relatively rigid frame for receiving said tube with the liner inserted therein, a stop at one end of said frame for the liner, another stop at the same end of the frame for said tube, said stops being l spaced apart to permit the end of the liner to project from the tube, plungers attached to said frame and adapted to be inserted therein and retracted from opposite ends of the liner, means attached to said relatively rigid frame and adapted to engage the outer surface of the walls of said tube at spaced points thereon for restraining said tube in a predetermined position with respect to said plungers, .said means comprising set screws mounted in spaced relatiom on said frame, means preventing leakage of iiuid between the walls of the liner and said plungers consisting of expansible cup-shaped members upon said plungers, means for introducing fluid underpressure through one of said vplungers to the space within the liner between said plungers, said means consisting of a rod mounted on one of said plungers having an opening running the length thereof and suitable means for connecting said rodV opening to the pressure supply, and means for venting undesirable uid from said liner, said means consisting of a similar rod mounted upon the other of said plungers having an opening running the length thereof.

2. An apparatus for expanding liners into tubes which comprises, in combination, a relatively rigid frame adapted to receive said tube with the liner inserted therein, rocker supporting members mounted at the rearward end of said frame and adapted to facilitate the tipping thereof, a stop at one end of said frame for the liner, another stop at the same end of the frame for said tube, said stops being spaced apart to permit the end of the liner to project from the tube, plungers attached to said frame and adapted to be inserted therein and retracted from opposite ends of the liner, means attached to said relatively rigid frame and adapted to engage the outer surface of the walls of said tube at spaced points thereon for restraining said tube in a predetermined position with respect to said plungers, said means comprising set screws mounted in spaced relation on said frame, means preventing leakage of uid between the walls of the liner and said plungers consisting of. expansible cup-shaped members upon said plungers, means for introducing uid under pressure through one of said plungers to the space Within the liner between said plungers, said means consisting of a rod mounted on one of said plungers having an opening running the length thereof and suitable means for connecting said rod opening to the pressure supply, and means for venting undesirable uid froml said liner, said means consisting of a similar rod mounted on the other of said plungers having an opening running the length thereof,

EDWIN C. LEONHARDY. 

